Low profile flat wet electrolytic tantalum capacitor

ABSTRACT

A low profile wet electrolytic capacitor is disclosed. The low profile wet electrolytic capacitor includes an outer case assembly. The outer case assembly is formed by an outer case and outer case cover that is hermetically sealed to the outer case. The outer case assembly includes an interior area. A capacitive element is positioned in the interior area. The capacitive element is isolated from the outer case assembly by a plurality of insulative elements. A connecting tube is positioned perpendicular to and attached to the outer case and the outer case cover and passes through an opening in the capacitive element. An isolated positive lead is positioned on the outer case assembly and is in electrical communication with the capacitive element. A fluid electrolyte is contained in the interior area of the outer case assembly. A method of forming the capacitor and stacked capacitor assemblies is also provided.

FIELD OF INVENTION

This application relates to the field of electronic components, and morespecifically, capacitors.

BACKGROUND

Wet capacitors are used in the design of circuits due to theirvolumetric efficiency, stable electrical parameters, high reliabilityand long service life. Such capacitors typically have a largercapacitance per unit volume than certain other types of capacitors,making them valuable in high-current, high-power, and low-frequencyelectrical circuits. One type of wet capacitor is a wet electrolyticcapacitor. A wet electrolytic capacitor includes two conducting surfaces(an anode and a cathode) whose function is to conduct electricity, and afluid electrolyte. An insulating material or dielectric separates thetwo conducting surfaces. Wet electrolytic capacitors tend to offer agood combination of high capacitance and low leakage current.

Wet electrolytic capacitors are basic to various types of electricalequipment from satellites, aerospace, airborne, military group support,oil exploration, power supplies, and the like. In any of these exampleapplications, the capacitor may be exposed to harsh environmentalconditions, including extreme temperatures, pressure, moisture, shock,vibration, and the like. The capacitor must be able to withstand theseharsh environmental conditions while maintaining its accuracy, servicelife, and ability to be powered at very high temperatures with nomaintenance. Failure of a capacitor due to harsh environmentalconditions would necessitate its removal for repairs, which would resultin delays and other associated expenses. Additionally, many of theseexample applications include significant dimensional or layoutconstraints, as the field of electronics is consistently demandingsmaller parts and devices. For example, reductions in both mounting areaand component profile (i.e., height) are highly demanded in most currentapplications.

Known wet electrolytic capacitors, such as Tantalum (Ta) electrolyticcapacitors, are generally characterized as having a cylindrical shapeand axial leaded terminations. Tantalum electrolytic capacitors known inthe art may use tantalum for the anode material. The tantalum anode body(also commonly referred to as a “slug” or “pellet”) is usually sintered.A wire (which may also be formed of tantalum) is commonly formed in theanode body in one of two ways: (1) “embedded,” meaning the wire iscovered with tantalum powder during a pressing process; or (2) “welded,”meaning after the pellet is pressed and sintered, the wire is welded tothe tantalum anode body. The other end of the wire extends outside ofthe tantalum anode body. The capacitor dielectric material may be madeby anodic oxidation of the anode material to form an oxide layer overthe surface of the anode body (e.g., Ta to Ta₂O₅). A capacitor cathodemay be formed by coating an inner surface of the body or case of thecapacitor that encloses the tantalum anode body. The cathode may beformed of sinter tantalum or electrophoretically deposited tantalum, andmay be attached to a cathode wire. A fluid electrolyte separates thecathode and the anode body and provides for electrical communicationbetween the cathode and anode body. Although cylindrical shapedcapacitors with axial leaded terminations generally perform reliably inharsh environmental conditions, their provided energy density is limitedby their cylindrical shape and limited surface area of their conductingsurfaces (anode and cathode), as the surface area of the two conductingsurfaces determines the capacitance of the capacitor. Additionally,dimensional constraints often make their application difficult.

Other types of known wet electrolytic capacitors are characterized ashaving a circular or square shaped capacitor body or “can” with radialleaded terminations. While circular or square shaped capacitors withradial leaded terminations may provide higher energy density whencompared to cylindrical shaped capacitors with axial leadedterminations, their ability to operate in harsh environmental conditionsis limited. For example, circular or square shaped capacitors withradial leaded terminations generally are more susceptible to elevatedtemperatures that cause capacitor swelling. Additionally, circular orsquare shaped capacitors with radial leaded terminations generally havelimited ability to survive in high shock or vibration environments.

Thus, there remains a need for an improved wet electrolytic capacitorcapable of operating in harsh environmental conditions characterized byhigh energy density and a low profile to comply with common dimensionalconstraints.

SUMMARY

In one aspect of the present invention, a low profile wet electrolyticcapacitor is disclosed. The low profile wet electrolytic capacitorincludes an outer case assembly. The outer case assembly is formed by anouter case and outer case cover that is hermetically sealed to the outercase. The outer case assembly includes an interior area. A capacitiveelement is positioned in the interior area. The capacitive element isisolated from the outer case assembly by one or more insulativeelements. A connecting tube is positioned perpendicular to and attachedto the outer case and the outer case cover and passes through an openingin the capacitive element. An isolated positive lead is positioned onthe outer case assembly and is in electrical communication with thecapacitive element. A negative terminal is positioned on the outer caseassembly. A fluid electrolyte is contained in the interior area of theouter case assembly.

The present invention is also directed to, in another aspect, multiplelow profile wet electrolytic capacitors mounted in a capacitor stack.Multiple low profile wet electrolytic capacitors may be mounted in astacked formation or capacitor stack and electrically connected to oneanother in parallel or in series.

A method of making a low profile wet electrolytic capacitor is alsoprovided. A method of making a low profile wet electrolytic capacitormay preferably comprise the steps of: forming an outer case defining aninterior area; forming an outer case opening in a wall of the outercase; positioning an insulator band around a perimeter of the interiorarea of the outer case; forming a connecting tube; welding theconnecting tube to the outer case at the outer case opening; positioningan insulator tube over the connecting tube; forming an outer case cover;forming an outer case cover opening in a wall of the outer case cover;positioning a first and second cathode layer on an internal surface ofthe outer case and the outer case cover; forming a capacitor element;positioning the capacitive element in the interior area of the outercase; welding the outer case cover to the outer case and connectingtube; positioning a positive lead insulator over the outer case; weldinga positive lead over the positive lead insulator to the cathode element;and welding a negative terminal to the outer case.

A method of making a low profile wet electrolytic capacitor stackassembly having a plurality of capacitors electrically connected to oneother in parallel or in series is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1 is an isometric view of a capacitor according to an embodiment ofthe present invention;

FIG. 1A is an enlarged detailed view of the area defined by 1A in FIG.1;

FIG. 2 is a left side view of a capacitor according to an embodiment ofthe present invention;

FIG. 3 is a cross-sectional view from the top of the capacitor accordingto an embodiment of the present invention taken along line 3-3 of FIG.2;

FIG. 3A is an enlarged detailed view of the area defined by 3A in FIG.3;

FIG. 4 is a cross-sectional view from the bottom of the capacitoraccording to an embodiment of the present invention taken along line 4-4of FIG. 2;

FIG. 4A is an enlarged detailed view of the area defined by 4A in FIG.4;

FIG. 5 is an exploded view of a capacitor case and case wall assemblyaccording to an embodiment of the present invention;

FIG. 6 is an exploded view of an anode assembly according to anembodiment of the present invention;

FIG. 7 is an isometric view of several capacitors mounted in a stackedformation and connected in parallel according to an embodiment of thepresent invention;

FIG. 8A is an isometric view of several capacitors mounted in a stackedformation and connected in series according to an embodiment of thepresent invention;

FIG. 8B is an isometric view of several capacitors mounted in a stackedformation and connected in series according to an embodiment of thepresent invention;

FIG. 9 is a flow diagram of a process for assembling a capacitoraccording to an embodiment of the present invention;

FIG. 10 is a flow diagram of a process for making the capacitor elementaccording to an embodiment of the present invention;

FIG. 11 is a flow diagram of a process for assembling a capacitoraccording to an embodiment of the present invention;

FIG. 12 is a flow diagram of a process for assembling a stackedcapacitor assembly connected in parallel according to an embodiment ofthe present invention; and

FIG. 13 is a flow diagram of a process for assembling a stackedcapacitor assembly connected in series according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right,” “left,” “top,” and “bottom”designate directions in the drawings to which reference is made. Thewords “a” and “one,” as used in the claims and in the correspondingportions of the specification, are defined as including one or more ofthe referenced item unless specifically stated otherwise. Thisterminology includes the words above specifically mentioned, derivativesthereof, and words of similar import. The phrase “at least one” followedby a list of two or more items, such as “A, B, or C,” means anyindividual one of A, B, or C, as well as any combination thereof.

FIGS. 1-6 show a capacitor 100 according to an embodiment of the presentinvention. Referring to FIGS. 1, 2, and 5, the capacitor 100 includes anouter case assembly 105 comprising an outer case 102 and outer casecover 104. The outer case 102 may be formed of metal, such as tantalum(Ta) and forms part of the cathode of the capacitor 100. The outer case102 has a front side 106, a rear side 108, a left side 110, a right side112, and a top 114. The outer case 102 preferably has an open end asshown in FIG. 5. The outer case cover 104 may be formed of the samemetal as the outer case 102 (i.e., tantalum if tantalum is also used asthe material of the outer case 102), and may be hermetically welded tothe open end of the outer case 102 as shown in FIG. 5. The outer casecover 104 also forms part of the cathode. While the shape of the outercase 102 may vary, in an embodiment of the present invention and asshown in FIGS. 1-4, the sides 106, 108, 110, 112 may have a generallyrectangular shape, and the top 114 may have a generally square overallshape. When the outer case cover 104 is hermetically welded to the outercase 102, the outer case assembly 105 is formed.

The outer case 102 further comprises an outer case opening 103 which maypreferably be formed centrally in the top 114 of the outer case 102. Theouter case cover 104 further comprises an outer case cover opening 107which may preferably be formed centrally in the outer case cover 104,and is sized and positioned to align with the outer case opening 103.The outer case 102 further comprises an anode termination opening 111.

The outer case assembly 105 has a length L, a width W, and a height H.As shown in FIGS. 1, 2, and 5, the outer case assembly 105 forms agenerally flat rectangular or square cuboid or prism with an interiorarea 109 or cavity. The sides 106-112 and top 114 of the outer case 102may also have rounded or beveled edges at the corners 116. The ratio ofwidth W to height H of the outer case assembly 105 should preferably beat least 4:1 to provide a low profile and to allow for the greatestamount of surface area of the conducing surfaces (i.e., anode andcathode). However, varying ratios, that are greater or less than 4:1,may be used to comply with dimensional constraints. The shape andconstruction of the outer case 102 assists in providing improved energydensity over known capacitors while also providing a reduced height orprofile that is advantageous in applications where height availabilityfor components is limited.

As shown in FIGS. 1-6, the outer case 102 further includes a positivelead 120 disposed on the left side 110 over the anode terminationopening 111. The positive lead 120 may be a metal plate, preferablyformed of nickel (Ni) or a nickel (Ni) alloy. It should be noted thatthe positive lead 120 may comprise other materials as appreciated by aperson of skill in the art. A positive lead insulator 122 may beprovided between the positive lead 120 and the outer case 102 over theanode termination opening 111 to provide electrical isolation betweenthe outer case 102, which is negative and forms part of the cathode ofthe capacitor 100, and the positive lead 120 which is positive. Thepositive lead insulator 122 may be formed from a material comprisingpolytetrafluoroethylene (PTFE). However, it is appreciated that thepositive lead insulator 122 may comprise any non-conductive flexiblematerial, and may be formed of materials such as Teflon or Kapton. Theouter case 102 further includes a negative terminal 121 disposed on thefront side 106 of the outer case 102. The negative terminal 121 may be ametal plate, preferably formed of a nickel weldment. It should be notedthat the negative terminal 121 may comprise other materials asappreciated by a person of skill in the art. While the outer caseassembly 105 forms the cathode (i.e., the negative electrode), thenegative terminal 121 is attached to the outer case 102 of the outercase assembly 105 in order to provide for a convenient and reliableconnection point to connect the capacitor 100 to an electrical circuit.

As shown in FIGS. 3, 3A, and 5, one side of the outer case 102, and inthe illustrated examples, the rear side 108 of the outer case 102,includes a fill port 125 and a fill port cover 124. The fill port cover124 may be formed from a valve metal, such as tantalum, titanium orniobium. In a preferred embodiment, the fill port cover 124 is formedfrom tantalum. The fill port cover 124 may be welded in place to theouter case 102 over the fill port 125 and a fill port plug 123 toeffectively seal the fill port 125. The fill port 125 is used forintroducing an electrolyte into an interior area of the outer case 102during manufacture.

The fill port 125 and fill port plug 123, or variations thereof that maybe used, are discussed in U.S. patent application Ser. No. 14/942,011,the entire contents of which are incorporated by reference herein. Itshould be noted that the fill port 125 may alternatively be formed inanother position along the outer case 102 without departing from thescope of the present invention.

As shown in FIGS. 1, 3, 4, and 6, the capacitor 100 also preferablyincludes a connecting tube 118. The connecting tube 118 may be formed ofmetal, such as tantalum, and functions to connect the top 114 of theouter case 102 and the outer case cover 104 to prevent the outer case102 and outer case cover 104 from expanding or contracting duringexposure to harsh environmental or use conditions, such as, for example,extreme temperatures.

The connecting tube passes through the outer case opening 103 and theouter case cover opening 107. The connecting tube 118 may be connected,joined, or otherwise bonded to the outer case 102 and outer case cover104, for example, adjacent the outer case opening 103 and the outer casecover opening 107, in a variety of ways known to those of skill in theart. Preferably the connecting tube 118 will be hermetically welded tothe outer case 102 and outer case cover 104 adjacent the outer caseopening 103 and the outer case cover opening 107. While the shape of theconnecting tube 118 may vary, in an embodiment of the present inventionand as shown in FIGS. 1, 3, 4, and 5, the connecting tube 118 may have acylindrical tube shape having a hollow passage. The connecting tube 118may also be connected to the approximate center of the outer case 102and the outer case cover 104, however, it may alternatively be disposedin an off-center position, such as if the position of the outer caseopening 103 and the outer case cover opening 107 are changed to adifferent position.

As shown in FIGS. 3-6, a capacitive element 126 is provided in theinterior area 109 of the outer case assembly 105. The shape and the sizeof the capacitive element 126 may generally be slightly less than thatof the outer case assembly 105 in order to provide for increased energydensity, i.e., a large surface area. The capacitive element 126 (whichmay also be referred to in the art as an “anode body,” “slug,” or“pellet”) may preferably be formed as a sintered, tantalum slug or solidpellet anode body, or may comprise other materials as appreciated by aperson of skill in the art, such as niobium (Nb) or niobium monoxide(NbO). The capacitive element 126 is positioned in the interior area 109and isolated from the outer case assembly 105 by one or more of theinsulative elements, e.g., the first and second separator sheets 134 a,134 b, insulator tube 136, and/or insulator band 138.

The capacitive element may include a dielectric layer 127, preferablytantalum pentoxide (Ta₂O₅) made by anodic oxidation of the capacitiveelement 126 to form an oxide layer over the surface of the capacitiveelement 126 (e.g., Ta to Ta₂O₅). Tantalum pentoxide possesses a highdielectric strength and a high dielectric constant. The dielectric layer127 may be of varying thicknesses, depending on the target workingvoltage of the capacitor. The capacitive element 126 is immersed in afluid electrolyte 140 held within the interior area 109 of the outercase assembly 105.

As shown in FIGS. 3, 3A, and 6, an anode wire 128 is provided extendingfrom a side of the capacitive element 126. The anode wire 128 may beimbedded in, welded to, or otherwise connected, joined, or bonded to,the capacitive element 126. The anode wire 128 may preferably be formedof tantalum, or may comprise other materials as appreciated by a personof skill in the art. The anode wire 128 comprises a portion of the anodeof the capacitor 100, and is in electrical communication with thecapacitive element 126. As shown in FIGS. 3, 3A, and 6, the anode wire128 is connected to a lead wire 129. In a preferred embodiment, theanode wire 1289 is welded to the lead wire 129. The lead wire 129 alsocomprises a portion of the anode of the capacitor 100. The lead wire 129may be formed of tantalum. The lead wire 129 extends through the outercase 102 at the anode termination opening 111, and provides electricalcommunication between the capacitive element 126, the anode wire 129,and positive lead 120. A glass-to-metal seal (GTMS) 130 is positioned atthe interior of the outer case 102 at approximately the position of thepositive lead 120 and anode termination opening 111. The GTMS 130 may behermetically welded on the interior side of the outer case 102 toeffectively connect the lead wire 129 and the positive lead 120. TheGTMS includes a conductive metal outer portion 131 formed from a metal,preferably tantalum, and a non-conductive inner portion 133 formed fromglass. The lead wire 129 is positioned through the non-conductive innerportion 133. The non-conductive inner portion 133 of the GTMS 130assists in isolating the lead wire 129 (and connected anode wire 128),from the outer case assembly 105. The GTMS 130 also functions to assistin sealing the outer case assembly 105 at the anode termination opening111.

As shown in FIGS. 4, 4A, and 6, a first and second cathode layer 132 a,132 b are positioned on the internal surface of at least a portion ofthe outer case assembly 105, and may be formed from tantalum foil coatedwith palladium (Pd). The first and second cathode layers 132 a, 132 bare separated from the capacitive element 126 by first and secondseparator sheets 134 a, 134 b. The first and second separator sheets 134a, 134 b may be formed from an electrolytic permeable materialcomprising polytetrafluoroethylene (PTFE), or some other non-conductivematerial. The first and second separator sheets 134 a, 134 b function toprevent contact between the anode elements (capacitive element 126,anode wire 128, lead wire 129) and the cathode elements (first andsecond cathode layers 132 a, 132 b and outer case assembly 105).

Similarly, as shown in FIGS. 3-5, an insulator tube 136 and an insulatorband 138 are positioned within the outer case 102 to prevent contactbetween the anode elements (capacitive element 126, anode wire 128, leadwire 129), and the cathode elements (first and second cathode layers 132a, 132 b and outer case assembly 105) and connecting tube 118. Theinsulator tube 136 is positioned over and covers the outer surface ofconnecting tube 118 that connects the outer case 102 and the outer casecover 104. The insulator tube 136 forms an isolative barrier between thecathode elements (first and second cathode layers 132 a, 132 b and outercase assembly 105) and the capacitive element 126. The insulator tube136 may be formed from a material comprising polytetrafluoroethylene(PTFE), or some other non-conductive material.

The insulator band 138 is positioned around at least part of theinternal perimeter of sides 106-112 of the outer case 102 and forms anisolative barrier between sides 106-112 of the outer case 102 and thecapacitive element 126. As shown in FIG. 5, the insulator band 138 maynot be a closed band and may include a gap to accommodate the anode wire128, lead wire 129, GTMS 130, and associated termination at the positivelead 120. The insulator band 138 may be formed from a materialcomprising PTFE, or some other non-conductive material.

The low profile of capacitor 100 (due to the ratio of width to height ofouter case assembly 105 preferably being at least 4:1) allows forcompact mounting onto a printed circuit board (PCB). Additionally, thelow profile of capacitor 100 allows for compact and easy mounting ofseveral capacitors into a capacitor stack (connected in parallel or inseries) to achieve increased total capacitance value and/or higheroperating voltage while maintaining a low profile.

Referring to FIG. 7, there is shown a plurality of capacitors 200 a, 200b, . . . , 200 n mounted in a stacked formation, which may be referredto as a “capacitor stack.” In the embodiment of FIG. 7, the capacitors200 a, 200 b, . . . , 200 n are stacked in the same orientation, so thatthe positive leads 220 a, 220 b, . . . , 220 n and the negativeterminals 221 a, 221 b, . . . , 221 n are aligned on the same respectivesides. As shown in FIG. 7, capacitors 200 a, 200 b, . . . , 200 n areelectrically connected in parallel to increase total capacitance value.Each of the plurality of capacitors 200 a, 200 b, . . . , 200 n in thestack are connected via a positive termination 240 at each capacitor'srespective positive lead 220 a, 220 b, . . . , 220 n. The positivetermination 240 may have a generally planar shape, and may be shapedlike a strip. The positive termination 240 may be connected to eachcapacitor's respective positive lead 220 a, 220 b, . . . , 220 n in avariety of ways known to one of skill in the art, but will preferably bewelded to each capacitor's respective positive lead 220 a, 220 b, . . ., 220 n. The positive termination 240 is preferably formed as a thinpiece of generally planar and/or generally rectangular metal, preferablyformed of nickel or nickel alloys. However, it should be noted that thepositive termination 240 may be of a different shape and/orconfiguration.

Each of the plurality of capacitors 200 a, 200 b, . . . , 200 n in thestack are also connected via a negative termination 245 at eachcapacitor's negative terminal 221 a, 221 b, . . . , 221 n. The negativetermination 245 may have a generally planar shape, and may be shapedlike a strip. The negative termination 245 may be connected to eachcapacitor's respective negative terminal 221 a, 221 b, . . . , 221 n ina variety of ways known to one of skill in the art, but will preferablybe welded to each capacitor's negative terminal 221 a, 221 b, . . . ,221 n. The negative termination 245 is preferably formed as a thin pieceof generally planar and/or generally rectangular metal, preferablyformed of nickel or nickel alloys. However, it should be noted that thenegative termination 245 may be of a different shape and/orconfiguration. The openings 107 of the plurality of capacitors 200 a,200 b, . . . , 200 n in the stack are preferably aligned at a centrallocation of the stack.

As shown in FIG. 7, one or more insulator sheets 250 may be positionedbetween each of the plurality of capacitors 200 a, 200 b, . . . , 200 n.The insulator sheet(s) 250 may be formed from an electrolytic permeablematerial comprising polytetrafluoroethylene (PTFE), or some othernon-conductive material.

Referring to FIGS. 8A and 8B, there is shown a plurality of capacitors300 a, 300 b, 300 c, 300 d mounted in a stacked formation. The viewshown in FIG. 8B is a 90 degree clockwise rotation of the view shown inFIG. 8A, so that all of the connecting terminations (positiveterminations and negative terminations) are illustrated. The pluralityof capacitors 300 a, 300 b, 300 c, 300 d are stacked in alternatingrotated orientations, such as 90 degree alternating rotated orientationsbetween adjacent capacitors in the stack, so that the positive leads 320a, 320 c and the negative terminals 321 a, 321 c of the first and thirdcapacitor 300 a, 300 c, are aligned and on the same side of thecapacitor stack, and the positive leads 320 b, 320 d and the negativeterminals 321 b, 321 d of the second and fourth capacitor 300 b, 300 dare aligned and on the same side of the capacitor stack. Stated anotherway, capacitors 300 a and 300 c will be oriented identically andcapacitors 300 b and 300 d will be oriented identically.

Although four (4) capacitors are illustrated, more or less than four (4)capacitors may be stacked, and the use of four (4) capacitors is onlyfor the purposes of illustration. As shown in FIGS. 8A and 8B,capacitors 300 a, 300 b, 300 c, 300 d are electrically connected inseries to achieve higher operating voltage. A first positive termination340 a connects the positive leads 320 a, 320 c of capacitor 300 a and300 c. The first positive termination 340 a may be connected to thepositive leads 320 a, 320 c of capacitor 300 a and 300 c in a variety ofways known to one of skill in the art, but will preferably be welded tothe positive leads 320 a, 320 c of capacitor 300 a and 300 c. The firstpositive termination 340 a is preferably formed as a thin piece ofgenerally planar and/or generally rectangular metal, preferably formedof tantalum. A first isolator 350 a may be positioned between the firstpositive termination 340 a and the outer case of capacitor 300 b. Theisolator 350 a may be formed of Teflon, Kapton or other electricallyisolative material. A second positive termination 340 b connects thepositive leads 320 b, 320 d of capacitor 300 b and 300 d. The secondpositive termination 340 b may be connected to the positive leads 320 b,320 d of capacitor 300 b and 300 d in a variety of ways known to one ofskill in the art, but will preferably be welded to the positive leads320 b, 320 d of capacitor 300 b and 300 d. The second positivetermination 340 b is preferably formed as a thin piece of generallyplanar and/or generally rectangular metal, preferably formed oftantalum. A second isolator 350 b may be positioned between the secondpositive termination 340 b and the outer case of capacitor 300 c. Thesecond isolator 350 b may be formed of the same material as firstisolator 350 a.

Similarly, a first negative termination 345 a connects the outer case(cathode) at the negative terminals 321 b, 321 d of capacitor 300 b and300 d. The first negative termination 345 a may be connected to thenegative terminals 321 b, 321 d of capacitor 300 b and 300 d in avariety of ways known to one of skill in the art, but will preferably bewelded to the negative terminals 321 b, 321 d of capacitor 300 b and 300d. The first negative termination 345 a is preferably formed as a thinpiece of generally planar and/or generally rectangular metal, preferablyformed of tantalum. A third isolator 350 c may be positioned between thefirst negative termination 345 a and the outer case of capacitor 300 c.The third isolator 350 c may be formed of the same material as isolators350 a, 350 b. A second negative termination 345 b connects the outercase (cathode) at the negative terminals 321 a, 321 c of capacitor 300 aand 300 c. The second negative termination 345 b may be connected tothenegative terminals 321 a, 321 c of capacitor 300 a and 300 c in avariety of ways known to one of skill in the art, but will preferably bewelded to the negative terminals 321 a, 321 c of capacitor 300 a and 300c. The second negative termination 345 b is preferably formed as a thinpiece of generally planar and/or generally rectangular metal, preferablyformed of tantalum. A fourth isolator 350 d may be positioned betweenthe second negative termination 345 b and the outer case of capacitor300 b. The isolator 350 d may be formed of the same material asisolators 350 a-350 c.

As shown schematically as flow diagrams in FIGS. 9-11, a method ofmanufacturing a capacitor according to the invention is also provided.

As illustrated in FIG. 9, first, the outer case assembly is prepared. Anouter case 102 is formed [400], having an open end and interior area109. An outer case opening 103 is formed in a top wall of the outer case102 and an anode termination opening 111 is formed in a sidewall of theouter case [402]. A fill port 125 is formed in a wall of the outer case102 [404]. An insulator band 138 is positioned around at least part ofthe interior perimeter of the outer case 102 [406]. A connecting tube118 is formed [408]. The connecting tube 118 is welded to the outer case102 at the outer case opening 103 [410]. An insulator tube 136 ispositioned over the outer surface of connecting tube 118 [412]. An outercase cover 104 is formed [414]. An outer case cover opening 107 isformed in a wall of the outer case cover 104 [416]. A first and secondcathode layer 132 a, 132 b are positioned on the internal surface of theouter case 102 and the outer case cover 104 [418].

As illustrated in FIG. 10, a capacitive element of the capacitor is alsoprepared. First, the capacitive element 126 is formed as a sintered,tantalum slug [420]. An anode wire 128 is connected to the capacitiveelement 126 [422]. In a preferred embodiment, the anode wire 128 iswelded to the capacitive element 126. The anode wire 128 is connected toa lead wire 129 and positioned through a GTMS 130 [424]. A first andsecond separator sheet 134 a, 134 b are positioned on both sides of thecapacitive element 126 [426].

Steps for capacitor assembly are illustrated in FIG. 11. The capacitiveelement 126 and first and second separator sheets 134 a 134 b arepositioned inside the interior area 109 of the outer case 102 [428]. TheGTMS 130 is welded into place on the interior side of the outer case 102[430]. The outer case cover 104 is welded to the outer case 102 and tothe connecting tube 118 [432]. A positive lead insulator 122 is placedover the outer case 102 over the anode termination opening 111 at thetermination point of the lead wire 129 [434]. A positive lead 120 isplaced over the positive lead insulator 122 and welded to the lead wire129 [436]. A fluid electrolyte is introduced into the interior area 109through the fill port 125 [438]. A fill port plug 123 is placed againstthe fill port 125 [440]. A fill port cover 124 is placed over the fillport plug 123 and the fill port 125, compressing the fill port plug 123into the fill port 125, and the fill port cover 124 is welded in placeto the outer case 102 [442].

Steps for stacked capacitor assembly connected in parallel areillustrated in FIG. 12. A plurality of capacitors 200 a, 200 b, . . . ,200 n are provided. The plurality of capacitors 200 a, 200 b, . . . ,200 n, are placed in a stacked formation with an insulator sheet 250placed between the opposing surfaces of each of the plurality ofcapacitors 200 a, 200 b, . . . , 200 n [500]. A positive termination 240is welded to each capacitor's respective positive lead 200 a, 220 b, . .. , 220 n [502]. A negative termination 245 is welded to eachcapacitor's negative terminals 221 a, 221 b, . . . , 221 n [504].

Steps for stacked capacitor assembly connected in series are illustratedin FIG. 13. A plurality of capacitors 300 a, 300 b, 300 c, 300 d areprovided. The plurality of capacitors 300 a, 300 b, 300 c, 300 d areplaced in a stacked formation in alternating rotated orientations, sothat the positive leads 320 a, 320 c and the negative terminals 321 a,321 c of the first and third capacitor 300 a, 300 c, are on the sameside, and the positive leads 320 b, 320 d and the negative terminals 321b, 321 d of the second and fourth capacitor 300 b, 300 d are on the sameside [600]. A first positive termination 340 a is positioned over afirst isolator 350 a, positioned between the first positive termination340 a and the outer case of capacitor 300 b, and is placed over andwelded to the positive leads 320 a, 320 c of capacitor 300 a and 300 c[602]. A second positive termination 340 b is positioned over a secondisolator 350 b, positioned between the second positive termination 340 band the outer case of capacitor 300 c, and is placed over and welded tothe positive leads 320 b, 320 d of capacitor 300 b and 300 d [604]. Afirst negative termination 345 a is positioned over a third isolator 350c, positioned between the first negative termination 345 a and the outercase of capacitor 300 c, and is placed over and welded to the negativeterminals 321 b, 321 d of capacitor 300 b and 300 d [606]. A secondnegative termination 345 b is positioned over a fourth isolator 350 d,positioned between the second negative termination 345 b and the outercase of capacitor 300 b, and is placed over and welded to the negativeterminals 321 a, 321 c of capacitor 300 a and 300 c [608].

Although the features and elements of the present invention aredescribed in the example embodiments in particular combinations, eachfeature may be used alone without the other features and elements of theexample embodiments or in various combinations with or without otherfeatures and elements of the present invention.

What is claimed is:
 1. A low profile wet electrolytic capacitor,comprising: an outer case assembly defining an interior area andcomprising an outer case and outer case cover hermetically sealed to theouter case; a capacitive element positioned in the interior area andisolated from the outer case assembly; a connecting tube positionedperpendicular to and attached to the outer case and the outer case coverand passing through an opening in the capacitive element; an isolatedpositive lead positioned on the outer case assembly in electricalcommunication with the capacitive element; a negative terminalpositioned on the outer case assembly; and a fluid electrolyte containedin the interior area of the outer case assembly.
 2. The low profile wetelectrolytic capacitor of claim 1, wherein the outer case assembly has aratio of width to height of at least 4:1.
 3. The low profile wetelectrolytic capacitor of claim 1, further comprising one or moreinsulative elements configured to isolate the capacitive element fromthe outer case assembly, wherein the insulative elements comprise afirst separator sheet and a second separator sheet positioned on a firstand second side of the capacitive element.
 4. The low profile wetelectrolytic capacitor of claim 3, wherein the insulative elementsfurther comprise an insulator band positioned around at least part of aninterior of the outer case assembly.
 5. The low profile wet electrolyticcapacitor of claim 4, wherein the insulative elements further comprisean insulator tube positioned over and covering an outer surface of theconnecting tube.
 6. The low profile wet electrolytic capacitor of claim1, further comprising a first and second cathode layer positioned on theinternal surface of at least a portion of the outer case assembly. 7.The low profile wet electrolytic capacitor of claim 1, wherein thecapacitive element comprises tantalum.
 8. The low profile wetelectrolytic capacitor of claim 1, wherein the outer case assemblycomprises tantalum.
 9. The low profile wet electrolytic capacitor ofclaim 1, further comprising: an anode wire connected to the capacitiveelement at a first end and the isolated positive lead at a second endvia a lead wire, wherein the anode wire and the lead wire facilitate theelectrical communication between the isolated positive lead and thecapacitive element.
 10. The low profile wet electrolytic capacitor ofclaim 1, wherein the low profile wet electrolytic capacitor is mountedin a capacitor stack with at least one other capacitor.
 11. The lowprofile wet electrolytic capacitor of claim 10, wherein the low profilewet electrolytic capacitor is mounted in the capacitor stack with the atleast one other capacitor in the same orientation.
 12. The low profilewet electrolytic capacitor of claim 10, wherein the low profile wetelectrolytic capacitor is mounted in the capacitor stack with the atleast one other capacitor in alternating rotated orientations.
 13. Thelow profile wet electrolytic capacitor of claim 10, wherein the lowprofile wet electrolytic capacitor is electrically connected to the atleast one other capacitor in parallel.
 14. The low profile wetelectrolytic capacitor of claim 10, wherein the low profile wetelectrolytic capacitor is electrically connected to the at least oneother capacitor in series.
 15. A method of making a low profile wetelectrolytic capacitor, the method comprising: forming an outer casedefining an interior area; forming an outer case opening in a wall ofthe outer case; positioning an insulator band around a perimeter of theinterior area of the outer case; forming a connecting tube; welding theconnecting tube to the outer case at the outer case opening; positioningan insulator tube over the connecting tube; forming an outer case cover;forming an outer case cover opening in a wall of the outer case cover;positioning a first and second cathode layer on an internal surface ofthe outer case and the outer case cover; forming a capacitor element;positioning the capacitive element in the interior area of the outercase; welding the outer case cover to the outer case and connectingtube; positioning a positive lead insulator over the outer case cover;welding a positive lead over the positive lead insulator to the cathodeelement; welding a negative terminal to the outer case.
 16. A lowprofile wet electrolytic capacitor stack, comprising: a plurality of lowprofile wet electrolytic capacitors mounted in a stack formation,wherein each of the plurality of low profile wet electrolytic capacitorscomprises: an outer case assembly defining an interior area andcomprising an outer case and outer case cover hermetically sealed to theouter case; a capacitive element positioned in the interior area andisolated from the outer case assembly; a connecting tube positionedperpendicular to and attached to the outer case and the outer case coverand passing through an opening in the capacitive element; an isolatedpositive lead positioned on the outer case assembly in electricalcommunication with the capacitive element; a negative terminalpositioned on the outer case assembly; and a fluid electrolyte containedin the interior area of the outer case assembly.
 17. The low profile wetelectrolytic capacitor stack of claim 16, wherein the plurality of lowprofile wet electrolytic capacitors are mounted in the stack formationin the same orientation.
 18. The low profile wet electrolytic capacitorstack of claim 16, wherein the plurality of low profile wet electrolyticcapacitors are mounted in the stack formation in alternating rotatedorientations.
 19. The low profile wet electrolytic capacitor stack ofclaim 16, wherein each of the plurality of low profile wet electrolyticcapacitors are electrically connected in parallel.
 20. The low profilewet electrolytic capacitor stack of claim 16, wherein at least one ofthe plurality of low profile wet electrolytic capacitors is electricallyconnected to at least another one of the plurality of the low profilewet electrolytic capacitors in series.